This project studies the role of interleukin-10 (IL-10) in uveitis. Uveitis was induced in mice by subcutaneous injection of bacterial endotoxin. Intraocular inflammation was assessed by leukocyte count and protein concentration measurement in the aqueous humor. Mouse recombinant IL-10 or its vehicle alone were administered by repeated intravenous injections. In four of five experiments, the cellular infiltration in the eye was significantly reduced. The number of cells was reduced by 62 percent, 64 percent, 48 percent, 11 percent, and 40 percent, respectively, in the group treated with IL-10 compared with the control group. IL-10 did not affect protein exudation. We conclude that systemic administration of IL-10 has an anti- inflammatory effect acting on the cellular component of the immune response in endotoxin-mediated uveitis.